1. Field of the Invention
The present invention relates to an image display device, and more particularly to an image display device displaying an image by applying laser light onto a projected plane.
2. Description of the Background Art
Image display devices displaying images by applying laser light onto projected planes such as screens or walls include so-called laser projectors. In a laser projector, laser lights of three primary colors of red, green and blue need to be prepared in order to reproduce images in full color. The configurations concerning image display using laser light in this manner are proposed in the followings.
Japanese Patent Laying-Open No. 2003-005110 discloses an apparatus two-dimensionally scanning light, in which projection of a pattern used for sensing the quantity of light is prevented.
Japanese Patent Laying-Open No. 2007-057555 discloses an image display device capable of displaying high-quality images with brightness variations sufficiently reduced using a plurality of light beams.
Japanese Patent Laying-Open No. 2007-003687 discloses a configuration to display images by two-dimensionally scanning luminous flux modulated based on image information and emitted from light source means.
Japanese Patent Laying-Open No. 2006-133558 discloses a configuration for easily displaying images of high resolution and images having many gradation levels, with accurate gradation.
Japanese Patent Laying-Open No. 2003-172900 discloses a configuration to promote size and weight reduction and cost reduction of a projector apparatus and to alleviate the effect of a light source on vision by simplifying a basic structure.
It is known that when a laser diode is powered for a long time, the temperature of the laser diode itself changes and thus the response characteristic changes with the temperature change. In other words, the output power of light with respect to the level of current applied to the laser diode for driving decreases with increasing temperature. As a result, the quantity of light which should be achieved for a prescribed gradation at room temperature cannot be achieved at a time of a temperature rise, so that the image quality of display images is reduced. Therefore, it has been desired that the image quality of display images is appropriately maintained irrespective of such a response characteristic change.
In this respect, Japanese Patent Laying-Open No. 2003-005110 proposes that special pattern information is prepared, the quantity of light output by driving a laser diode according to the pattern information is monitored, and the reference value of the driving current of the laser diode is updated based on the monitor result. However, special pattern information needs to be prepared. Moreover, special control is required so that an image according to the pattern information is not displayed, thereby complicating the configuration.
Furthermore, Japanese Patent Laying-Open Nos. 2007-057555 and 2007-003687 show a configuration in which the quantity of applied beam light is detected and driving of a laser diode is controlled according to the detection result. However, such a response characteristic change of a laser diode is not considered in correction.
Japanese Patent Laying-Open Nos. 2006-133558 and 2003-172900 do not show control of driving of a laser diode considering such a response characteristic change of a laser diode, either.